Liquid crystal display is constituted of a polarizing plate and a liquid crystal cell.
The most widely used TFT liquid crystal display of TN-mode has an optical compensation film inserted between the polarizing plate and the liquid crystal cell to realize a high display quality of the liquid crystal display as described in JP-A-8-50206. However, such a display has the disadvantage that the thickness of the liquid crystal display itself increases.
JP-A-1-68940 describes that use of an elliptic polarizing plate having a retardation film on one side of a polarizer and a protective film on the other side thereof improves front-face contrast of the liquid display without increasing the thickness thereof. However, it was apparent that the retardation film (optical compensation film) of the invention disclosed in JP-A-1-68940 is liable to cause retardation by thermal strain or other causes, and thus has the problem on durability. This retardation causes framelike light leakage (increase of transmittance) to deteriorate the display quality of the liquid crystal display.
To suppress occurrence of the retardation by strain, JP-A-7-191217 and EP-0911656A2 directly use an optical compensation film formed by applying an optical anisotropic layer comprising a discotic compound on a transparent support as a protective film for the polarizing plate, thereby solving the above-described problems on the durability without increasing thickness of the liquid crystal display.
However, it was found that when the polarizing plate using the optical compensation film as the protective film was set on a large panel of 17-inch or larger, it is impossible to completely prevent the light leakage caused by the thermal strain. The optical compensation film should have not only the function of compensating optically the liquid cell but also sufficient durability against change of service environments.